Issued  December  22, 1910. 


U.  S.  DEPARTMENT  OF  AGRICULTURE. 


FARMERS’  BULLETIN  421. 


THE  CONTROL  OF  BLOWING 

SOILS. 


K.  EC.  FREE, 

Physicist ,  Bureau  of  Soils , 

AND 

J.  M.  WESTGATE, 

Agronomist ,  Bureau  of  Plant  Industry. 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 

1910. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Washington,  D.  C.,  August  21,  1910. 

Sir:  We  have  the  honor  to  transmit  herewith  and  to  recommend  for  publication  as 
a  Farmers’  Bulletin  the  manuscript  of  an  article  entitled  “The  Control  of  Blowing 
Soils,”  prepared  by  Mr.  J.  M.  Westgate,  Agronomist  in  the  Bureau  of  Plant  Industry, 
and  Mr.  E.  E.  Free,  Physicist  in  the  Bureau  of  Soils. 

The  rapid  extension  of  agricultural  operations  into  the  sections  of  the  United  States 
where  the  rainfall  is  so  limited  as  to  make  the  problem  of  soil  blowing  a  serious  one 
has  led  to  numerous  calls  for  information  concerning  the  best  methods  of  solution. 
Both  the  Bureau  of  Plant  Industry  and  the  Bureau  of  Soils  have  published  technical 
papers  dealing  with  the  respective  phases  of  the  problem.  It  is  thought  advisable, 
however,  in  the  present  paper,  to  give  the  views  of  both  bureaus  in  a  single  publication. 

Respectfully, 


Hon.  James  Wilson, 

Secretary  of  Agriculture. 


Milton  Whitney, 

Chief,  Bureau  of  Soils. 
G.  H.  Powell, 

Acting  Chief,  Bureau  of  Plant  Industry. 


CONTENTS. 


Page. 


Introduction .  3 

Normal  movements  of  the  soil . 3 

Causes  of  excessive  blowing  of  soil . . .  5 

Control  of  soil  blowing .  7 

Blowing  of  sandy  soils . 12 

Blowing  of  newly  cleared  lands . *. .  15 

Blowing  of  other  soils .  17 

Miscellaneous  problems .  18 

Control  of  drifting  sand  and  sand  dunes .  21 

Summary . , .  23 


ILLUSTRATIONS. 

Page. 


Fig.  1.  Dust  storm  in  the  Great  Plains  region .  6 

2.  Asparagus  field  protected  by  low  windbreaks  of  sagebrush .  8 

3.  Windbreaks  of  Lombardy  poplar  trees  protecting  valuable  orchards 

along  the  Columbia  River  in  Oregon .  9 

4.  Roots  of  a  tree  exposed  by  excessive  blowing .  12 

5.  Newly  set  strawberry  field  in  sandy  soil .  13 

6.  The  same  field  illustrated  in  figure  5,  showing  the  effect  of  wind  on 

the  newly  set  strawberry  plants .  14 

7.  Young  orchard  injured  by  an  incursion  of  sand  from  an  adjacent  newly 

cleared  field . 15 

8.  Blow-out  in  a  sandy  pasture  induced  by  overgrazing  and  trampling, 

followed  by  strong  winds .  20 

9.  Planting  beach-grass  to  protect  Cape  Cod  Harbor  (Massachusetts)  from 

drifting  sand  dunes .  21 

10.  Sand  fence  holding  an  otherwise  shifting  sand  dune  in  place .  22 

421 

2 


B.  P.  I.— 614. 


THE  CONTROL  OF  BLOATING  SOILS. 


INTRODUCTION. 

The  problem  of  blowing  soils  is  important  wherever  there  are 
considerable  areas  of  bare  soil  exposed  to  the  continued  action  of 
relatively  high  winds  without  accompanying  rainfall.  In  the  more 
sandy  sections  even  frecpient  rains  do  not  suffice  to  hold  the  soil 
in  sufficient  check  to  entirely  prevent  blowing.  The  most  important 
problem  is  the  prevention  of  soil  blowing  on  bare  fields  or  on 
fields  so  recently  seeded  that  the  crops  have  not  made  sufficient 
growth  to  protect  the  surface.  Other  problems,  such  as  the  pre¬ 
vention  of  soil  blowing  in  cuts,  embankments,  etc.,  are  sometimes 
important,  but  in  the  aggregate  are  much  less  so  than  the  more 
widely  extended  blowing  which  occurs  on  ordinary  cultivated  fields. 
Nearly  all  cases  of  injury  by  blowing  can  be  cured  or  greatly  bettered 
without  undue  expense  if  the  farmer  has  an  understanding  of  the 
practical  means  of  control. 

It  is  only  where  there  is  excessive  blowing  of  the  soil  that  damage 
occurs.  There  is  a  normal  and  moderate  movement  of  the  soil  by 
wind,  the  effects  of  which  are  probably  more  beneficial  than  other¬ 
wise  in  mixing  the  soil  and  renewing  the  upper  surface.  It  constitutes 
one  factor  which  tends  to  maintain  the  fertility  of  any  particular  soil. 

.  NORMAL  MOVEMENTS  OF  THE  SOIL. 

Careful  investigation  has  shown  that  the  soil  is  in  constant  change. 
Water  and  wind  are  always  moving  soil  material  from  place  to  place, 
removing  here,  depositing  there,  with  a  net  tendency  toward  its  slow 
transfer  from  the  land  surface  into  the  sea.  The  share  of  water  in 
this  movement  of  soil  is  well  known,  but  that  of  the  wind  is  less 
apparent.  In  the  deserts,  however,  the  frequent  dust  storms  and 
the  constant  shifting  of  sand  over  the  surface  have  in  the  aggregate 
great  and  well-known  geologic  actions.  Similarly,  'in  sand-dune 
areas,  on  coasts  and  elsewhere,  the  effects  of  the  wind  are  obvious. 
Even  in  the  humid  regions  the  wind  plays  no  inconsiderable  part 
in  the  general  process  of  soil  movement,  but  its  actions  are  here 
so  slow  that  they  usually  escape  attention  and  are  recognized  by 
421  3 


4 


THE  CONTROL  OF  BLOWING  SOILS. 


indirect  evidence  alone.  Among  the  items  of  this  evidence  may 
be  mentioned  the  well-known  tendency  of  dust  to  gather  in  unused 
rooms,  on  the  beams  of  barns,  and  in  similar  places  to  which  it 
could  have  been  carried  only  through  the.  air.  Analyses  of  these 
various  dusts  have  shown  them  to  be  simply  ordinary  soil,  and 
if  enough  soil  to  be  noticeable  is  accumulated  in  such  places  much 
more  must  be  blowing  about  continually  in  the  open  fields.  Similarly, 
partly  melted  snowdrifts  have  always  a  dirty  appearance,  espe¬ 
cially  if  they  have  lain  for  some  time.  This  dirt,  too,  is  blown  soil, 
and  much  more  must  be  in  motion  in  the  summer,  when  the  ground 
is  more  fully  exposed,  though  there  is  then  no  indicator,  such  as  the 
snow,  to  show  its  presence. 

This  continual  blowing  of  small  quantities  of  soil  is  naturally  greater 
on  cultivated  fields  than  elsewhere,  as  there  is  no  protective  covering 
of  vegetation.  The  reality  of  the  phenomena  may  be  shown  by  a 
very  simple  experiment.  If  any  ordinary  glass  partly  full  of  water 
be  placed  for  a  few  days  on  a  fence  (or  other  support)  in  the  midst 
of  cultivated  fields,  the  water  will  become  muddy  from  soil  which 
blows  into  it,  and  this  will  occur  when  the  wind  movement  is  only 
normal.  On  very  windy  days  the  quantity  of  dust  collected  will 
be  much  greater. 

The  moving  of  soil  by  wind  and  water,  and  even  its  final  removal 
into  the  sea,  is  not  in  general  harmful.  Much  good  results  from 
this  process.  Were  the  soil  a  stationary  thing,  and  did  each  partic¬ 
ular  soil  grain  remain  forever  in  one  place,  fertility  would  rapidly 
decrease.  The  removal  of  plant  food  materials  by  plants  and  in  the 
drainage  waters  would  ultimately  take  from  the  upper  layers  of 
the  soil  much  of  the  elements  useful  to  plants.  The  soil,  however, 
is  not  stationary;  its  surface  layers  are  being  continually  removed 
by  wind  and  water  and  the  particles  carried  (mainly  by  the  water) 
to  the  sea.  In  their  stead  new,  unweathered,  and  unexhausted 
fragments  of  the  underlying  rocks  are  coming  into  the  soil  zone 
and  in  their  turn  are  contributing  to  its  fertility.  This  process  of  the 
removal  of  worn-out  soil  must  of  course  be  properly  balanced  against 
the  agencies  of  chemical  rock  decay  and  the  extraction  of  nutrients  by 
plants.  If  the  mechanical  removal  of  soil  material  be  too  slow, 
there  will  be  an  actual  chemical  exhaustion.  If  it  be  too  rapid, 
there  will  not  be  time  for  the  necessary  weathering  and  preparation 
of  the  rock  fragments  which  appear  from  below.  Both  of  these  ex¬ 
tremes  occur  in  nature,  the  second  far  more  often  than  the  first,  but 
fortunately  both  are  comparatively  rare. 

As  one  of  the  agents  of  a  properly  balanced  removal,  the  wind  is 
frequently  of  great  importance,  but  even  in  places  where  its  tendency 
is  not  to  .remove  but  to  leave  the  surface  level  unchanged,  or  even  to 

421 


THE  CONTROL  OP  BLOWING  SOILS. 


5 


cause  deposition,. it  may  still  have  a  beneficial  influence  upon  soil  fer 
tility.  The  drift  of  blown  material  back  and  forth  will  tend  to  mix  with 
each  other  all  the  surface  soils  of  the  area  affected  and  may  thus  sup¬ 
ply  in  some  places  useful  minerals  in  which  the  soil  there  happens  to 
be  deficient,  but  which  were  present  in  more  than  needful  quantity  in 
other  soils  of  the  area.  Similarly,  by  removing  fertile  material  from 
deserts  and  depositing  it  in  other  and  often  distant  regions,  the  wind 
has  built  and  is  building  many  large  areas  of  soil  of  great  fertility  and 
high  agricultural  value.  Examples  of  these  are  the  loess  soils  of 
China  and  Central  Asia  and  the  “tirs,”  or  black  earth,  of  Morocco. 
Some  of  the  very  fertile  loess  soils  of  the  Mississippi  Valley  are  prob¬ 
ably  also  wind-deposited. 

The  normal  degree  of  soil  movement  by  the  wind  is,  therefore,  more 
beneficial  than  harmful.  Local  conditions  may,  however,  be  such 
that  wind  erosion  becomes  excessive,  and  grave  injury  is  done  to  both 
crops  and  soil.  With  the  opening  up  of  much  land  in  the  arid  and 
semiarid  regions,  this  danger  of  wind  damage  has  become  of  vital 
importance  to  American  agriculture.  It  is  to  an  outline  of  the  most 
useful  known  methods  of  avoiding  this  injury  that  the  present  bulletin 
is  devoted. 


CAUSES  OF  EXCESSIVE  BLOWING  OF  SOIL. 

The  two  factors  involved  in  the  blowing  or  shifting  of  the  soil  by  the 
wind  are  the  strength  of  the  wind  and  the  power  of  the  soil  to  resist 
its  action.  When  the  wind  strength  becomes  too  great  for  the  resist¬ 
ing  powers  of  the  soil,  blowing  will  occur.  (See  fig.  1.) 

Some  soils  blow  very  easily  and  are  damaged  by  light  winds. 
Ordinarily,  however,  the  soil  has  a  fair  power  of  resistance,  and  it  is 
only  from  heavy  winds  that  serious  damage  may  be  expected.  The 
likelihood  of  damage  over  any  given  area  will  depend  upon  the  fre¬ 
quency  of  heavy  winds  there,  and  especially  upon  the  frequency  cf 
such  winds  during  the  season  (usually  the  spring)  when  the  soil  is 
least  protected  by  vegetation  or  snow  and  most  open  to  attack. 

The  velocity  of  the  wind  is  not,  however,  the  only  factor  which 
affects  the  problem.  Its  direction  and  constancy,  as  well  as  the 
moisture  content  of  air  and  soil,  etc.,  are  also  of  importance.  For 
instance,  a  wind  constant  in  direction  from  day  to  day  will  do  far 
more  damage  to  agricultural  land  than  variable  winds,  which  undo 
to-day  what  they  did  yesterday.  Also  a  moist  wind,  or  a  wind  fol¬ 
lowing  a  rain  which  has  left  the  soil  well  wetted,  will  do  comparatively 
little  harm. 

The  resistance  of  a  soil  to  wind  action  depends  upon  its  cohesion 
and  its  degree  of  exposure  to  the  wind.  The  cohesion  is  to  a  certain 
extent  controlled  by  the  physical  and  chemical  nature  of  the  soil,  but 

421 


6 


THE  CONTROL  OF  BLOWING  SOILS. 


much  more  largely  by  its  water  content.  Thus,  a  clay  soil  is  less 
subject  to  blowing,  not  so  much  because  clay  particles  hang  together 
better  than  those  of  sand,  though  this  is  of  some  importance,  as 
because  the  water-holding  power  of  clay  is  better,  and  it  is  therefore 
more  likely  to  be  able  to  keep  itself  moist.  It  is  only  a  dry  soil,  or  one 
which  can  be  dried  by  the  wind,  that  will  blow  seriously.  The 
exposure  of  a  soil  is  even  more  important  than  its  cohesion.  If  the 
wind  is  unable  to  get  at  the  soil  there  can  be  no  blowing,  no  matter 
how  dry  or  loose  the  soil  or  how  strong  the  wind.  In  nature  the 

degree  of  exposure  de¬ 
pends  almost  entirely 
upon  vegetation.  If 
a  soil  is  well  covered, 
the  lower  layers  of 
moving  air  are  -en¬ 
tangled  in  the  plants 
and  retarded,  and  the 
air  next  the  soil  has 
only  a  very  low  ve¬ 
locity.  The  “wind” 
does  not  reach  the  soil 
at  all.  For  this  rea¬ 
son,  and  because  of 
the  actual  holding  of 
the  soil  by  plant  roots, 
a  cover  of  vegetation 
is  a  nearly  perfect 
protection  against 
blowing. 

It  is  obvious  that 
both  of  the  soil  fac¬ 
tors  affecting  blow¬ 
ing,  namely,  cohesion 
and  exposure,  are 
mainly  controlled  by  the  water  supply.  A  moist  soil  is  always  coher¬ 
ent,  and  a  dry  one  is  only  seldom  so  when  loose.  Similarly  the  cov¬ 
ering  of  vegetation  (native  or  artificially  planted)  which  a  soil  will 
bear,  and  hence  the  degree  of  protection  with  which  it  can  provide 
itself,  sustains  a  direct  and  closely  corresponding  relation  to  the  water 
supply.  It  is  to  be  expected,  therefore,  that  soil  blowing  will  be  an 
especially  serious  problem  in  regions  of  low  rainfall.  In  the  arid 
region,  soil  blowing  is  the  rule,  while  in  the  humid  regions  it  occurs 
only  in  exceptional  cases,  mainly  on  sandy  soils  of  very  low  cohesion 
and  situated  in  windy  regions. 

421 


Fig.  1. — Dust  storm  in  the  Great  Plains  region.  In  this  storm,  last¬ 
ing  twelve  horns,  at  least  one  inch  of  topsoil  was  removed. 


THE  CONTROL  OF  BLOWING  SOILS. 


7 


Damage  by  soil  blowing  may  be  and  usually  is  twofold:  Directly, 
to  the  soil,  and  indirectly,  to  the  plant  or  crop  covering.  The  injury 
to  the  soil  itself  is  usually  through  removal,  and  there  are  many  cases 
in  which  the  blowing  away  of  the  fertile  surface  layers  exposes  sub¬ 
soils  insufficiently  weathered  and  filled  with  humus  to  be  ready  for 
crops.  More  generally  important,  however,  are  the  injuries  to  the 
crop  itself  by  blowing  out  or  burial,  or  the  direct  cutting  effect  of 
flying  sand  grains.  The  danger  is  especially  great  to  new  seedings  or 
plantings,  since  a  great  proportion  of  the  ground  is  bare  and  unpro¬ 
tected.  It  is  no  uncommon  occurrence  for  farmers  in  the  arid  and 
semiarid  sections  to  lose  an  entire  crop  through  the  blowing  out  of 
the  seed  or  the  uprooting,  burial,  or  cutting  off  of  the  young  plants. 
After  the  plants  are  larger  they  become  not  only  better  able  to  sur¬ 
vive  burial  or  exposure  of  roots,  but  also  more  efficient  in  covering 
and  holding  the  soil  and  preventing  its  blowing. 

CONTROL  OF  SOIL  BLOWING. 

MEANS  OF  PREVENTING  DAMAGE. 

It  is  apparent  from  the  facts  just  stated  that  the  means  by  which 
the  damage  may  be  prevented  or  decreased  must  be,  in  principle, 
two:  (1)  Increasing  the  cohesion  of  the  soil,  and  (2)  decreasing  its 
exposure  to  the  wind.  The  cohesion  may  be  increased  practically  (1) 
by  increasing  the  water  content  of  the  soil,  (2)  by  increasing  the 
amount  of  humus  which  it  contains,  and  (3)  by  modifying  its  texture, 
as,  for  instance,  by  adding  clay  or  by  leaving  it  in  small  clods  instead  of 
in  a  finely  pulverized  condition.  The  exposure  may  be  decreased  (1) 
by  providing  a  cover  of  growing  vegetation,  (2)  by  leaving  the  stubble 
of  the  last  crop  still  standing  on  the  land,  (3)  by  providing  an  arti¬ 
ficial  cover  of  straw,  brush  lines  (fig.  2),  etc.,  and  (4)  by  planting 
windbreaks  to  protect  the  fields.  (See  fig.  3.)  In  addition  to  the 
above  methods,  the  roughening  of  the  surface  by  proper  cultivation 
really  protects  the  finer  soil  particles  from  blowing,  as  they  soon 
become  located  in  the  depressions,  where  the  exposure  to  the  winds 
is  much  less. 

The  degree  of  usefulness  of  these  various  general  methods  of  con¬ 
trol  in  any  particular  case  depends  upon  local  conditions  of  soil  char¬ 
acter,  climate,  the  lay  of  the  land,  etc.  All  of  them  are  in  use  under 
various  circumstances  and  in  varied  combinations.  Indeed,  most 
of  the  practical  expedients  employed  to  prevent  blowing  act  in  two 
or  three  of  these  ways,  frequently  leading  to  both  increase  of  cohesion 
and  decrease  of  exposure.  Some  of  the  practical  expedients  may  be 
outlined  as  follows. 


421 


8 


THE  CONTROL  OF  BLOWING  SOILS. 


SUITABLE  CROPPING  SYSTEM. 

Where  it  is  possible  to  do  so,  the  easiest  way  to  prevent  wind  dam¬ 
age  is  to  plan  the  use  of  the  land  so  that  it  will  always  be  covered 
with  some  form  of  protective  vegetation  during  the  season  when  dan¬ 
gerous  winds  are  to  be  expected.  Whether  this  can  be  economically 
done  depends  altogether  on  the  climate,  the  relation  to  markets,  the 
season  in  which  the  windy  periods  occur,  and  other  factors  of  the 
same  sort.  All  of  these  are  so  entirely  local  that  a  general  discussion 
is  impossible.  A  few  general  expedients  along  this  line  can,  however, 
usually  be  employed.  For  instance,  if  fall  plowing  is  not  necessary, 
the  stubble  of  the  last  crop  should  be  left  on  the  soil  until  as  late  as 


Fig.  2.— Asparagus  field  protected  by  low  windbreaks  of  sagebrush. 


possible  in  the  spring,  or  oats  or  barley  may  be  sowed  in  the  late 
summer  or  early  fall.  The  plants  will  be  killed  by  the  frost  and  will 
form  a  protective  mat  on  the  soil  surface.  This  will  prevent  blow¬ 
ing  during  the  winter  and  early  spring. 

In  other  cases  it  may  be  possible  to  combine  with  a  slow-growing 
crop  subject  to  wind  damage  a  more  rapid-growing  nurse  crop, 
which  forms  a  cover  very  soon  after  seeding  and  protects  the  other 
crop  during  its  early  life.  Thus  a  thin  seeding  of  rye  or  barley  may 
be  used  in  which  to  introduce  alfalfa. a  Another  useful  method  of 
introducing  alfalfa  and  similar  slow-starting  crops  is  to  drill  in  the  seed 

«See  Farmers’  Bulletin  339,  entitled  “Alfalfa,”  a  copy  of  which  may  be  obtained 
without  cost  upon  application  to  the  Secretary  of  Agriculture. 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


9 


in  high-cut  stubble  of  thinly  sown  millet  or  thickly  seeded  cane  or  Kafir 
corn.  The  advantage  of  such  a  procedure  is  that  this  stubble  does 
not  further  rob  the  soil  of  moisture  as  a  nurse  crop  does.  When  a 
nurse  crop  is  used,  the  seeding  must  be  very  light,  especially  in  the 
semiarid  regions,  as  the  idea  is  to  obtain  just  enough  nurse  plants  to 
hold  the  soil  from  blowing  and  at  the  same  time  not  to  rob  the  young 
seedlings  unduly  of  their  much-needed  moisture. 

One  cause  of  blowing  which  is  connected  with  the  cropping  system 
is  the  use  of  the  summer  fallow.  This  leaves  the  land  fully  exposed, 
and  if  dangerous  winds  are  to  be  expected  in  the  summer  it  is  usually 


Fig.  3. — Windbreaks  of  Lombardy  poplar  trees  protecting  valuable  orchards  along  the  Columbia  River 
in  Oregon.  The  trees  have  been  planted  in  rows  100  yards  apart  across  the  valley.  The  land  between 
them  is  entirely  free  from  blowing  sand. 


better,  if  enough  water  is  available,  to  replace  the  summer  fallow  by 
corn  or  a  leguminous  crop  (preferably  intertilled),  which  is  plowed 
under  in  the  fall.  If  there  is  not  enough  water  for  this,  it  may  in 
extreme  cases  be  necessary  to  let  the  stubble  stand  all  summer  instead 
of  plowing  it  under  in  the  spring.  Any  needed  harrowing  should  be 
done  so  as  to  damage  the  stubble  covering  as  little  as  possible. 
Another  method  is  to  seed  rows  of  coarse-growing  crops  at  intervals 
across  the  fallow  field  at  right  angles  to  the  direction  of  the  prevail¬ 
ing  winds.  Sandy  lands  are  most  likely  to  blow,  and  these  for¬ 
tunately  absorb  water  readily  without  spring  cultivation. 


60874°— Bull.  421—10 - 2 


10  1HE  CONTROL  OF  BLOWING  SOILS. 

SUITABLE  METHODS  OF  CULTIVATION. 

In  preparing  a  seed  bed  and  in  handling  a  summer  fallow,  if  it  be 
necessary,  there  are  certain  methods  of  cultivation  which  are  fre- 
quently  useful  in  decreasing  soil  blowing.  These  are  specially  im¬ 
portant  in  the  intermountain  regions  of  the  West,  where  control  by 
the  use  of  crops  is  usually  impossible  because  of  the  seasonal  dis¬ 
tribution  of  rainfall.  The  first  of  these  is  the  compacting  of  the 
surface  soil  by  rolling  or  otherwise.  This  acts  not  only  in  the  direct 
production  of  a  firmer  and  more  resistant  surface,  but  also  by  bet¬ 
tering  the  capillary  properties  of  the  soil  and  increasing  its  capacity 
to  draw  water  from  the  lower  layers  and  to  maintain  a  moist  sur¬ 
face  which  is  not  easily  blown.  This  very  fact,  however,  is  what 
makes  rolling  increase  the  surface  evaporation  so  greatly,  and  there¬ 
fore  prevents  its  use  when  conservation  of  the  soil  water  is  important. 

The  second  and  more  generally  useful  method  is  the  roughening  of 
the  surface.  If  a  field  is  in  danger  of  wind  damage  its  surface  should 
so  far  as  possible  be  left  covered  with  clods  and  the  furrows  be  run 
at  right  angles  to  the  direction  of  the  dangerous  winds.  A  rough, 
cloddy,  and  furrowed  surface  acts  in  the  same  way  as  vegetation  in 
preventing  the  rapid  movement  of  the  layer  of  air  next  to  the  ground, 
thus  protecting  the  soil.  When  small  patches  of  soil  in  Helds  com¬ 
mence  to  drift  with  the  wind  the  prompt  use  of  a  harrow  or  other 
implement  to  roughen  the  surface  of  the  blowing  areas  will  usually 
stop  the  damage  and  prevent  its  spreading  to  the  rest  of  the  field. 
Opening  up  furrows  with  a  corn  lister  across  the  field  at  right  angles 
to  the  prevailing  wind  will  reduce  the  injury  from  blowing  and  also 
serve  to  reduce  the  run-off  in  case  of  heavy  rains.  The  maintenance 
of  a  rough  surface  is  especially  important  when  a  soil  mulch  is 
necessary.  The  recent  rapid  development  of  so-called  dry  farming  and 
the  use  therewith  of  the  dust  mulch  have  caused  a  great  increase  of 
wind  damage.  The  use  of  such  a  mulch  means  the  complete  expos¬ 
ure  of  large  areas  to  the  wind  for  months  at  a  time.  This  difficulty 
can  be  met  by  maintaining  (when  the  physical  nature  of  the  soil 
will  allow)  a  mulch  of  small  clods  instead  of  fine  dust.  The  efficiency 
in  conserving  moisture  will  be  quite  as  great  and  the  field  surface 
will  be  rough  and  not  so  likely  to  blow. 

KEEPING  THE  SOIL  MOIST. 

A  moist  soil  is  very  little  subject  to  wind  action;  consequently,  if 
enough  irrigation  water  is  available  at  a  time  when  any  serious 
trouble  with  blowing  threatens,  it  can  be  met  by  immediately  irrigat¬ 
ing  the  areas  where  the  soil  is  being  shifted  by  the  wind.  Under 
some  circumstances  this  is  a  useful  procedure,  but  the  water  must 
be  applied  with  care  in  order  to  avoid  drowning  the  land.  Too  much 
water  may  be  quite  as  injurious  as  too  little. 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


11 


ADDING  HUMUS. 

The  more  organic  matter  a  soil  contains  the  greater  will  be  its  cohe¬ 
sion,  not  only  because  of  the  direct  action  of  the  organic  bodies  them¬ 
selves,  but  also  because  they  increase  the  water-holding  power  of  the 
soil  and  hence  its  ability  to  keep  its  surface  moist.  The  presence  of 
humus  is  therefore  a  powerful  protection  against  blowing,  and  many 
soils  can,  by  humus-forming  methods  of  cultivation,  be  rendered 
naturally  resistant  to  wind  action.  The  practical  means  to  this  end 
are  usually  the  plowing  under  of  green  crops  and  the  use  of  stable 
manure.  These  measures  are  nearly  always  applicable  to  the  sandy 
trucking  soils  of  the  East  and  in  a  measure  to  many  of  the  soils  in 
semiarid  and  irrigated  sections  where  intensive  farming  can  be  prac¬ 
ticed.  They  should  be  accompanied  on  all  soils  subject  to  blowing 
by  the  general  policy  of  leaving  on  the  land  and  incorporating  with 
the  soil  the  maximum  of  straw  and  stubble.  The  plowing  under  of 
a  crop  with  matted  roots  will  have  an  additional  value  in  preventing 
blowing  because  of  the  binding  power  of  the  roots.  Freshly  turned 
sod  acts  similarly,  and  therefore  newly  broken  sod  lands  in  the  semi¬ 
arid  sections  are  usually  comparatively  free  from  blowing  for  the 
first  two  or  three  years.  Thinly  sown  grasses  and  similar  crops  are 
sometimes  of  value  as  nurse  crops  because  of  this  binding  power  of 
their  roots. 

ARTIFICIAL  PROTECTORS. 

A  much-used  method  of  protecting  fields  in  windy  regions  is  the 
planting  of  rows  of  trees  or  bushes,  or  the  erection  of  fences,  as  wind¬ 
breaks.  They  have  the  great  advantage  that  they  not  only  protect 
the  soil  but  also  prevent  direct  injury  to  the  plants  by  strong  winds. 
However,  their  cost  is  relatively  high  and  the  percentage  of  idle  land 
is  considerable.  They  are  not,  therefore,  advisable  in  extensive  agri¬ 
culture,  and  practically  their  use  is  restricted  to  the  cultivation  of 
valuable  crops  such  as  fruits,  garden  vegetables,  etc.  In  these  cases 
they  will  nearly  always  be  found  profitable  for  protection  to  the  crop 
alone,  regardless  of  the  existence  or  nonexistence  of  danger  of  wind 
damage  to  the  soil. 

Windbreaks  are  usually  best  made  of  trees  or  high  bushes.  The 
particular  species  which  is  most  satisfactory  will  depend  in  every  case 
on  local  conditions.  The  tree  selected  should  be  one  which  is  in  full 
foliage  and  possesses  its  maximum  of  wind-resisting  power  at  the 
season  when  dangerous  winds  are  to  be  expected.  It  should  not  be 
of  such  a  nature  as  to  harbor  insect  pests  or  to  spread  by  its  root  sys¬ 
tem  out  into  the  adjoining  fields.  The  design  of  the  windbreak  sys¬ 
tem,  the  spacing  between  rows,  and  between  the  trees  of  a  row, 
depends  entirely  on  the  species  of  tree  or  bush  selected,  local  condi¬ 
tions  of  topography,  strength  and  direction  of  winds  (especially  the 

421 


12 


THE  CONTROL  OF  BLOWING  SOILS. 


constancy  of  this  direction),  crop  to  be  grown,  etc.  (See  fig.  3.) 
In  general,  the  protective  effect  of  a  windbreak  will  extend  to  from 
ten  to  twenty  times  its  height.  Care  should  be  taken  that  in  a  region 
of  sand  drift  the  windbreak  does  not  become  simply  a  collector  of 
sand  blown  in  from  elsewhere.  This  can  be  avoided  by  planting 
supplementary  lines  of  bushes  or  strips  of  grass  outside  the  regular 
windbreaks  in  the  direction  from  which  the  sand  is  coming.  The 
best  plan,  however,  is  to  stop  the  drift  of  sand  at  its  source,  if  possible, 
as  it  is  usually  necessary  to  do  this  in  the  end  in  any  case.  Wind¬ 
breaks  in  fruit  regions  should  be  so  designed  as  not  to  stop  the  air 
drainage  and  thus  increase  the  damage  by  frost. 

In  a  few  special  cases  of  very  intensive  cultivation  it  may  be  profit¬ 
able  to  employ  low,  close-set  brush  lines  (see  fig.  2),  hedges  or  fences, 


Fig.  4. — Roots  of  a  tree  exposed  by  excessive  blowing. 

or  covers  of  boards,  straw,  or  other  litter  applied  directly  to  the  soil. 
The  field  of  usefulness  of  these  is  very  limited.  Where  straw  is  abun¬ 
dant  its  use  may  be  profitable  for  ordinary  crops.  It  should  be 
loosely  scattered  over  the  soil,  using  as  much  as  1  to  2  tons  per  acre. 
This,  when  subsequently  turned  under,  adds  to  the  humus  content 
of  the  soil  and  in  itself  reduces  the  tendency  of  the  soil  to  blow. 

BLOWING  OF  SANDY  SOILS. 

Sandy  soils  are  especially  liable  to  damage  by  blowing,  not  only 
because  of  their  low  natural  cohesion  but  also  because  they  are  usually 
well  drained  and  retain  water  poorly  in  the  surface  layer,  and  hence 
lack  the  surface  moisture  which  is  a  great  preventive  of  blowing  on 
soils  composed  of  finer  materials.  (See  fig.  4.)  The  danger  of  blow¬ 
ing  must  always  be  borne  in  mind  in  reckoning  the  value  of  sandy 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


13 


lands  and  in  designing  for  them  a  proper  system  of  cropping.  (See 
figs.  5  and  6.)  On  them,  as  on  others,  the  proper  adjustment  of  the 
cropping  system  is  frequently  all  that  is  necessary  to  prevent  blowing. 
The  principles  which  must  govern  its  design  are  not  essentially  differ¬ 
ent  in  the  case  of  sandy  soils  from  those  outlined  for  soils  in  general 
in  the  preceding  section.  It  should  be  noted,  however,  that  the 
possibility  of  letting  the  stubble  of  one  crop  stand  until  the  ground  is 
ready  for  the  next  is  more  common  on  sandy  soils  than  on  others. 
Such  soils  absorb  water  readily,  and  the  main  reason  for  fall  plowing, 
namely,  the  increase  of  ability  to  absorb  moisture,  is  in  their  case 
absent.  The  use  of  windbreaks  offers  also  no  new  problems  on 


Fig.  5. — Newly  set  strawberry  field  in  sandy  soil. 


sandy  soils.  Whether  they  are  to  be  used  or  not  used  will  be  decided 
by  factors  with  which  the  texture  of  the  soil  has  little  to  do,  except 
that  of  course  this  texture  may  be  the  cause  of  the  trouble  which 
makes  some  method  of  control  necessary. 

Aside  from  the  cropping  system,  and  in  case  windbreaks  are  not 
advisable,  the  main  control  method  which  is  applicable  to  sandy 
lands  is  the  increase  of  humus  by  the  addition  of  organic  matter,  such  as 
manure  or  straw  or  by  the  plowing  under  of  some  green  crop.  Sands 
are  frequently  deficient  in  humus,  and  its  addition  not  only  aids  in 
preventing  blowing  but  increases  the  usually  low  water-holding  power 
and  betters  the  general  structure  of  the  soil.  Cases  are  rare  in  which 
sandy  soils  do  not  need  humus,  and  their  cultivation  should  always 

421 


14 


THE  CONTROL  OF  BLOWING  SOILS. 


be  so  carried  out  as  to  increase  this  constituent.  Blowing  may  fre¬ 
quently  be  prevented  by  this  means  alone. 

The  methods  of  cultivation  (rolling,  and  the  maintenance  of  a 
rough  surface)  advocated  for  decreasing  blowing  in  general  are  of  little 
use  on  sands.  The  cohesiveness  of  sand  is  slight,  even  when  packed, 
and  the  formation  or  preservation  of  clods  is  nearly  always  impos¬ 
sible.  Furrows  run  transverse  to  the  wind  may  be  occasionally  of 
use,  but  are  at  best  a  minor  means  of  control.  This  is  true,  also,  of 
artificial  moistening.  Water  runs  so  quickl}^  through  a  sandy  soil 
that  it  is  usually  impossible  to  keep  the  surface  moist  unless  the 


Fig.  6. — The  same  field  illustrated  in  fig.  5,  showing  the  effect  of  wind  on  the  newly  set  strawberry  plants. 


whole  soil  is  saturated — a  procedure  manifestly  impossible  if  the 
land  is  to  be  used. 

There  are  rare  cases  in  which  sandy  soils  can  be  bettered  by  irriga¬ 
tion  with  silt-laden  water.  The  fine  material  added  in  the  water 
decreases  the  sandiness  of  the  soil,  increases  its  water-holding  power, 
and  makes  it  less  liable  to  blowing.  Naturally  this  procedure  is 
practically  possible  only  where  the  silt-laden  water  is  easily  available, 
and  such  places  are  rare.  It  has  been  used  in  parts  of  the  Rio  Grande 
3  here  is,  however,  a  natural  change  which  takes  place  in 
sandy  soils  that  is  of  importance  in  this  connection.  Blown  sands 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


15 


are  usually  very  clean  and  contain  only  small  amounts  of  finer  material, 
the  reason  being  that  this  fine  material  is  blown  away  as  fast  as 
formed.  If,  however,  the  soil  be  protected  from  wind  action,  and  if 
it  be  at  the  same  time  exposed  to  weathering  under  ordinary  surface 
conditions,  the  fine  material  formed  by  the  natural  breaking  up  of  the 
sand  grains  will  remain  in  the  soil.  The  gradual  accumulation  of  this 
fine  material  will  render  the  soil  progressively  less  sandy.  This 
natural  betterment  of  protected  sands  is  very  important  in  dune 
fixation  and  in  the  protection  of  wind-exposed  sandy  soils  generally. 
Each  year  that  the  sand  remains  fixed  it  becomes  better  able  to 
protect  itself  and  to  resist  wind  attack. 

BLOWING  OF  NEWLY  CLEARED  LANDS. 


Some  of  the  most  injurious  cases  of  blowing  so  far  met  with  in  this 
country  are  those  which  follow  the  clearing  of  new  land  for  irrigation 


FrG.  7.— Young  orchard  injured  by  an  incursion  of  sand  from  an  adjacent  newly  cleared  field. 


in  the  desert  regions  of  the  West.  (See  fig.  7.)  These  soils  are  often 
loose  in  texture,  frequently  sandy,  and  nearly  always  low’  in  humus. 
They  are  therefore  unusually  susceptible  to  wind' action  and  are 
protected  from  complete  removal  only  by  their  native  cover  of  bunch 
grasses,  sagebrush,  creosote  bushes,  etc.  With  the  recent  increase 
of  irrigation  in  these  regions  much  of  the  native  vegetation  has  been 
removed,  in  many  cases  with  most  disastrous  results.  The  drifting  of 

421 


16 


THE  CONTROL  OF  BLOWING  SOILS. 


the  soil  becomes  immediately  so  bad  as  to  practically  prevent  any 
useful  agriculture.  Nor  is  the  damage  confined  to  the  land  which  has 
been  cleared.  Sand  from  this  land  will  blow  onto  other  fields,  where 
by  proper  precautions  the  blowing  has  been  avoided,  killing  the 
crops,  filling  irrigation  ditches,  and  damaging  the  soil.  A  careless 
farmer  may  thus  easily  ruin  not  only  his  own  land,  but  that  of  his 
neighbors  as  well. 

Once  this  condition  has  been  allowed  to  arise  it  requires  much 
time,  expense,  and  labor  to  correct.  By  proper  foresight,  however, 
and  by  the  use  of  necessary  precautions  to  prevent  the  start  of  drift, 
the  danger  can  be  largely  avoided.  Prevention  of  injury  is  far 
cheaper  than  the  subsequent  reclamation.  It  should  be  remembered 
also  that  the  danger  is  largely  one  which  accompanies  the  beginning 
of  cultivation.  Two  or  three  years’  use  of  the  land,  blowing  being 
prevented  and  attention  paid  to  the  production  of  humus,  will 
usually  so  improve  the  soil  that  wind  damage  is  much  less  to  be 
feared. 

The  best  general  method  of  avoiding  this  damage  by  the  wind  is 
to  clear  always  in  small  areas  at  a  time.  Wholesale  clearing  generally 
means  wholesale  drift  of  such  exposed  sandy  areas.  When  the  lay 
of  the  land  will  allow  it,  a  convenient  way  of  clearing  is  to  divide 
the  field  into  strips  20  to  30  feet  wide  and  transverse  to  the  usual  wind 
direction.  Only  the  alternate  strips  are  cleared,  and  not  until  these 
cleared  strips  are  brought  into  cultivation  and  a  satisfactory  stand 
of  some  crop  obtained  on  them  are  the  remaining  uncleared  strips 
cleared  in  turn.  By  this  scheme  the  strips  first  cleared  are  pro¬ 
tected  by  the  strips  of  native  vegetation  on  either  side,  while  those 
of  the  second  set,  when  cleared  in  their  turn,  are  protected  by  the 
crop  on  the  first  cleared  strips.  There  is,  of  course,  the  disadvantage 
that  the  clearing  must  be  done  in  two  sections  and  is  therefore  less 
economical,  and  that  for  the  first  year  or  two  there  is  much  idle  land, 
and  cultivation  is  difficult  and  expensive  because  broken  by  the 
uncultivated  strips.  Experience  has  shown,  however,  that  these 
disadvantages  are  outweighed  by  the  avoidance  of  blowing.  In  the 
sections  where  there  is  a  good  natural  grass  covering,  a  comparatively 
narrow  strip  of  sod  may  be  left  at  suitable  intervals,  which  may  be 
allowed  to  remain  indefinitely  if  necessary.  In  the  same  way  a 
relatively  narrow  strip  of  sagebrush  may  be  left  at  intervals  with¬ 
out  seriously  reducing  the  crop-producing  areas  so  protected.  In 
extreme  cases  such  narrow  strips  may  be  left  permanently  unculti¬ 
vated,  or  may  later  be  cleared  and  put  into  alfalfa. 

There  are  cases,  however,  in  which  the  leveling  necessary  for 
proper  irrigation  makes  impossible  this  method  of  clearing  in  strips. 
In  such  places  the  difficulty  can  frequently  be  met  by  planting 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


17 


a  quick-growing  crop  immediately  after  clearing.  If  it  be  arranged 
to  allow  time  for  the  growth  of  this  crop  between  the  time  of 
clearing  and  the  season  of  dangerous  winds,  all  trouble  can  usually 

e  has  been  found  very  useful  as  such  a 
coyer  crop.  Where  the  native  vegetation  is  of  a  character  to  yield 
much  brush  when  cut  and  dry,  this  brush  may  be  saved  after  clearing 
and  spread  loosely  over  the  cleared  land  to  prevent  blowing  until  a 
crop  has  had  time  to  start.  In  some  cases  also  it  may  be  possible 
by  continued  irrigation  following  clearing  to  keep  the  soil  moist  and 
thus  prevent  blowing.  Other  expedients  will  be  suggested  by  local 
conditions.  The  important  point  is  that  farmers  intending  to  clear 
and  cultivate  such  lands  should  recognize  the  danger  and  prepare  to 
meet  it  before  clearing  is  commenced.  Once  the  land  has  been  suc¬ 
cessfully  gotten  under  cultivation  attention  to  the  production  and 
maintenance  of  humus  will  usually  prevent  further  trouble. 

BLOWING  OF  OTHER  SOILS. 

On  less  sandy  soils — loams,  silts,  etc. — damage  by  blowing  is  much 
less  frequent  and  the  places  where  blowing  occurs  are  found  largely 
in  the  semiarid  regions  and  are  more  or  less  directly  caused  by  the 
dust  mulch,  the  summer  fallow,  and  similar  procedures  employed  as 
aids  toward  the  conserving  of  the  limited  water  supply.  With  the 
recent  rapid  spread  of  agriculture  in  these  regions  and  the  great 
increase  in  the  use  of  these  methods  of  moisture  conservation,  the 
number  of  cases  of  serious  blowing  has  greatly  increased.  In  these 
cases  it  may  be  impossible  entirely  to  prevent  wind  damage  without 
at  the  same  time  suffering  a  fatal  loss  of  water.  The  damage  can, 
however,  usually  be  minimized  by  designing  the  scheme  of  farm 
management  with  this  end  in  view.  The  leaving  of  the  stubble,  the 
use  of  nurse  crops,  and  the  other  methods  outlined  will  frequently 
be  found  valuable  in  combination  and  with  modifications  suited  to 
local  conditions.  Whether  a  green-manuring  crop  shall  replace  the 
summer  fallow  must  be  decided  largely  with  relation  to  the  water 
supply.  Such  a  crop  will  not  only  prevent  wind  erosion  (usually 
severe  in  the  case  of  the  summer  fallow),  but  will  in  nearly  every 
case  be  of  other  benefit  to  the  soil.  It  may,  however,  use  so  much 
of  the  meager  supply  of  water  that  its  use  is  impossible. 

As  above  described  for  sands,  and  indeed  for  all  soils  subject  to 
blowing,  the  addition  of  humus  is  a  valuable  and  not-to-be-neglected 
expedient.  Usually,  however,  loams  and  silts  are  not  so  deficient  in 
this  constituent  as  are  sands. 

The  expedient  which  finds  its  special  application  on  loams  and  silts 
is  the  maintenance  of  a  rough  surface.  On  such  soils  this  procedure 
is  comparatively  easy.  Clods  will  hold  together  and  furrows  retain 
their  shape  much  better  than  on  more  sandy  soils.  On  fields  subject 

421 


be  avoided  in  this  way.  By 


18 


THE  CONTROL  OF  BLOWING  SOILS. 


to  blowing  clods  should  never  be  broken  up  until  the  time  of  seeding 
and  not  then  unless  it  is  absolutely  necessary  to  do  so  to  insure  the 
proper  germination  and  growth  of  the  crop.  Furrows  when  used 
should  be  run  at  right  angles  to  the  prevailing  wind  direction,  and 
harrowing  or  shallow  disking,  also  transverse  to  the  wind  direction, 
is  often  of  use.  As  already  stated,  a  mulch,  if  used,  should  be  as  far 
as  possible  of  clods  rather  than  entirely  of  dust. 

In  addition  to  silt  soils  of  the  ordinary  types,  there  are  in  many 
parts  of  the  Western  States  valuable  soils  composed  in  great  part  of 
volcanic  ash.  Because  of  the  irregular  shape  and  “lightness”  of 
their  component  particles  these  soils  are  unusually  susceptible  to 
blowing,  and  frequently  need  to  be  artificially  protected  from  the 
wind  either  by  windbreaks,  light  covering  of  straw,  or  covers  of 
vegetation  during  the  windy  season.  The  addition  of  humus,  rough- 
surface  cultivation,  and  the  various  other  expedients  previously  sug¬ 
gested  will  be  found  of  use.  The  addition  of  humus  is  especially 
valuable.  Fortunately  each  year  of  cultivation  makes  these  soils 
better  able  to  protect  themselves.  Volcanic  ash  is  easily  disinte¬ 
grated,  and  especially  so  under  cultivation.  Fixation  for  a  few  years, 
with  proper  attention  to  the  addition  of  humus,  will  usually  so  change 
the  texture  of  the  soil  and  so  increase  its  cohesion  as  to  greatly 
decrease,  if  not  entirely  remove,  the  danger  of  blowing. 

MISCELLANEOUS  PROBLEMS. 

Although  the  principal  problems  of  the  control  of  soil  blowing  are 
in  the  sections  of  limited  rainfall  and  on  loose  and  incoherent  sands, 
yet  there  are  even  in  the  humid  sections  many  local  problems  which 
merit  attention.  While  these  special  problems  may  be  relatively 
unimportant,  yet  in  the  aggregate  over  the  entire  country  their 
seriousness  is  not  to  be  underrated. 

PROTECTION  OF  IRRIGATION  DITCHES,  EMBANKMENTS,  ETC. 

The  expense  incident  to  the  opening  up  of  an  irrigating  ditch  is  so 
great  that  it  is  important  that  all  means  be  used  to  prevent  the 
filling  up  of  the  same,  either  by  the  blowing  in  of  the  soil  from  the 
immediate  banks  or  by  the  blowing  of  soil  from  adjacent  areas. 
While  the  growth  of  trees  or  shrubs  may  serve  to  bind  the  immediate 
ditch  banks,  yet  such  a  hedge  may  prove  injurious  by  causing  the 
deposition  in  the  ditch  of  blown  sand  which  would  otherwise  be  car¬ 
ried  clear  across.  The  use  of  willows  is  objectionable  owing  to  their 
tendency  to  spread  into  the  ditch  itself.  The  proper  solution  of  this 
difficulty  would  appear  to  he  the  use  of  some  low-growing  plant 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


19 


which  will  form  a  dense  mass  near  the  surface  but  offers  little  obstruc¬ 
tion  to  the  wind  and  causes  but  little  deposition  of  the  sand  which  it 
carries.  Protection  from  blown-in  sand  can  be  provided  by  the 
erection  of  a  suitable  windbreak  at  such  a  distance  from  the  ditch 
that  sand  drifts  which  may  form  around  it  will  not  prove  troublesome. 
Better  still,  the  sand  drift  may  be  stopped  at  its  source.  Tamarisks, 
Russian  artemisias,  and  willows  can  be  used  for  this  windbreak, 
though  some  irrigation  is  usually  necessary,  especially  when  estab¬ 
lishing  them.  Where  the  ditch  runs  through  the  sagebrush  territory 
it  may  be  sufficient  to  leave  a  narrow  strip  of  uncleared  sagebrush 
on  each  side.  When  other  means  fail  the  banks  may  be  seeded  with 
rye,  which  can  be  followed  by  some  permanent  perennial  grass  if  the 
same  be  available,  or  the  rye  can  be  seeded  annually. 

The  protection  of  earth  dams  or  embankments,  the  sides  of  railway 
cuts,  etc.,  may  be  similarly  effected,  though  here  the  damage  is  more 
likely  to  be  from  washing  than  from  blowing,  and  is  outside  the 
province  of  this  bulletin. 

PROTECTION  OF  ROADS. 

The  protection  of  roadways  is  occasionally  necessary.  Erosion, 
both  by  wind  and  by  water,  has  in  many  recorded  instances  resulted 
in  the  lowering  of  highways  until  they  are  sometimes  many  feet  below 
the  level  of  the  surrounding  country.  In  the  extensive  loess  areas  of 
China  the  roads  have  sunk  sometimes  to  a  depth  of  50  feet,  with 
the  sides  approaching  the  vertical.  In  our  own  country  it  has  been 
noted  in  eastern  Washington  that  the  roads  have  been  lowered  2 
or  3  feet  within  recent  years,  apparently  by  the  blowing  away 
from  the  roadbed  of  clouds  of  dust  raised  by  passing  vehicles.  These 
injuries  are  so  slowly  produced  that  preventive  measures  are  usually 
impracticable.  The  use  of  windbreaks  along  the  roads  may  some¬ 
times  be  advantageous,  but  is  open  to  the  disadvantage  of  causing 
deep  snowdrifts  if  the  country  be  subject  to  heavy  winter  snows. 

INJURIES  TO  PASTURES. 

Wherever  pastures  are  located  on  soils  of  a  sandy  nature  or  others 
which  have  a  tendency  to  blow  there  is  always  danger  of  starting  blow¬ 
outs  which  may  increase  in  size  and  work  the  destruction  of  consider¬ 
able  areas  of  valuable  grazing  land.  (See  fig.  8.)  Not  only  are  the 
plants  uprooted  as  the  blow-out  enlarges,  but  the  other  vegetation  in 
the  path  of  the  drifting  soil  or  sand  is  buried.  These  blow-outs  are 
very  apt  to  follow  overgrazing,  which  may  so  reduce  the  vitality  of 
the  grasses  that  they  will  succumb  during  unfavorable  seasons  and 
allow  the  soil  to  commence  blowing.  Obviously  the  best  practice  is 
to  abstain  from  overpasturing.  When  the  injury  is  done  it  can  best 

421 


20 


THE  CONTROL  OP  BLOWING  SOILS. 


be  cured  by  removing  as  large  a  proportion  of  the  stock  as  possible 
and  checking  the  expansion  of  the  local  blow-outs  by  brush  coverings, 
under  which  rye  may  be  started,  to  be  followed  by  grasses,  low 
shrubs,  or  trees.  Exposed  spots  which  experience  shows  to  be  espe¬ 
cially  susceptible  to  blowing  should  be  put  permanently  into  trees, 
shrubs,  or  some  form  of  vegetation  which  will  not  be  grazed. 

BLOWING  OF  FROST-LOOSENED  SOILS. 


A  kind  of  blowing  occasionally  met  with,  though  rarely  of  impor¬ 
tance,  is  the  winter  blowing  of  frost-loosened  soils  in  the  Northern 
States.  This  can  usually  be  prevented  by  leaving  the  stubble  on  the 


Fig.  8.— Blow-out  in  a  sandy  pasture  induced  by  overgrazing  and  trampling.,  followed  by  strong  winds. 


land  during  the  winter,  or,  if  fall  plowing  be  thought  necessary,  by 
leaving  the  field  with  a  rough  surface.  The  stubble  or  the  rough 
surface  will  tend  to  retain  the  snow  and  the  snow  will  protect  the 
soil,  as  well  as  itself  furnishing  a  valuable  source  of  water  supply. 

BLOWING  FOLLOWING  TIMBER  CUTTING. 

Some  lands  are  so  exposed  or  so  sandy  that  they  can  be  pre¬ 
vented  from  blowing  only  by  a  permanent  cover  of  timber  or  shrub¬ 
bery.  On  such  the  cutting  of  the  native  timber  is  frequently  fol¬ 
lowed  by  the  formation  of  blow-outs  and  the  desolation  of  the  entire 
area.  These  cases  come  more  properly  under  the  well-known  sand- 
dune  problem,  the  means  of  handling  which  are  outlined  in  the  suc- 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


21 


ceeding  pages.  In  such  cases,  as  with  many  excessively  exposed  soils 
of  mountains  and  sea  beaches,  cultivation  in  the  ordinary  sense  is 
impossible. 


CONTROL  OF  DRIFTING  SAND  AND  SAND  DUNES. 


INJURY  FROM  DRIFTING  SANDS. 


In  many  places,  especially  in  deserts  and  on  lake  and  sea  beaches, 
there  are  large  accumulations  of  sand  which  the  wind  has  blown  into 
great  drifts  or  dunes,  sometimes  more  than  a  hundred  feet  in  height. 
These  have  a  tendency  to  shift  their  position  slowly,  burying  every¬ 
thing  in  their  path,  and  where  the  movement  of  such  sand  dunes 


Fig.  9. — Planting  beach-grass  to  protect  Cape  cod  Harbor  (Massachusetts)  from  drifting  sand  dunes. 


threatens  valuable  property  the  problem  of  their  control  is  of  great 
moment.  Along  seashores  the  harbors  are  especially  liable  to  danger 
from  this  injury.  Where  railroads  and  highways  are  forced  to  follow 
the  shoreline  or  river  course  along  which  such  dunes  occur  the  prob¬ 
lem  of  keeping  the  sand  off  the  roadbed  is  very  serious.  An  aggre- 
gate  of  over  $50,000  has  been  spent  in  protective  devices  for  the  pro¬ 
tection  of  Cape  Cod  (Massachusetts)  Harbor  alone.  (See  fig.  9.) 
In  Europe  large  sums  of  money  have  been  spent  in  dune  control, 
especially  along  the  Baltic  Sea  in  Germany  and  in  Gascony  along  the 
French  coast. 


421 


22 


THE  CONTROL  OF  BLOWING  SOILS. 


On  the  farms  subject  to  injuries  by  shifting  sand  dunes  the  prob¬ 
lem  is  important,  not  usually  because  of  the  value  of  the  dune  lands 
themselves,  but  because  of  the  danger  of  the  destructive  movement 
of  dunes  over  fertile  soil,  orchards,  or  farm  buildings.  The  farmer 
in  the  arid  regions  especially  finds  it  often  necessary  to  control  a 
sand  dune  because  of  its  menace  to  the  other  areas  of  his  farm. 

DEVICES  FOR  THE  CONTROL  OF  DRIFTING  SANDS. 


Trees  or  shrubs  are  usually  the  only  form  of  vegetation  capable  of 
producing  permanent  fixation  of  dune  sands,  and  the  ultimate  end 
arrived  at  by  nearly  all  systems  of  control  is  the  establishment  of  a 


Fig.  10.— Sand  fence  holding  an  otherwise  shifting  sand  dune  in  place. 


forest  or  tree  covering.  It  is  manifestly  impossible,  however,  to 
directly  establish  young  trees  upon  the  exposed  areas.  A  consid¬ 
erable  preliminary  protection  is  necessary.  Such  mechanical  devices 
as  brush  lines,  scattered  brush,  straw,  or  refuse  material  of  any  kind 
all  tend  to  temporarily  hold  the  sand  until  grass  or  other  herbaceous 
vegetation  can  be  established.  This  herbaceous  vegetation  will 
usually  give  sufficient  protection  to  the  young  trees  while  they  are 
obtaining  growth  enough  to  cover  the  ground  and  constitute  in 
themselves  a  permanent  protection.  A  method  which  has  proven 
very  effective  along  the  Columbia  River  and  elsewhere  is  to  make  a 
preliminary  seeding  of  rye  and  protect  it  by  a  thin  scattering  of  straw 

421 


THE  CONTROL  OF  BLOWING  SOILS. 


23 


over  the  surface.  At  10-foot  intervals  among  the  rye  are  put  sets 
of  permanent  sand-binding  grasses  which  spread  by  underground 
rootstocks.  These  grasses  are  usually  to  be  found  growing  on  the 
sandy  areas  in  the  neighborhood.  These  spread  and  establish  a 
permanent  grass  covering  by  the  time  the  rye  has  ceased  to  be  effec¬ 
tive.  If  a  good  stand  of  rye  is  secured  it  will  usually  reseed  itself 
for  several  years.  Following  the  permanent  grasses  and  by  their 
protection,  it  is  usually  possible  to  establish  shrubs  and  trees  at  suit¬ 
able  intervals.  The  tree  selected  should  be  of  a  kind  which  will  fur¬ 
nish  a  dense  growth  near  the  surface  of  the  ground  rather  than  a  tall 
trunk,  branchless  at  the  bottom.  Where  there  is  plenty  of  moisture 
in  the  soil,  willows  are  very  well  adapted  to  this  purpose.  Cotton¬ 
woods  are  of  perhaps  more  universal  application.  Pines  have  been 
much  used  abroad,  but  do  not  seem  to  be  adapted  to  American 
conditions. 

For  checking  the  movement  of  a  dune,  either  as  an  end  in  itself 
or  as  a  means  toward  forestation  or  fixation  with  grasses  or  other 
plant  covering,  a  particular  form  of  fence  has  proved  very  useful. 
This  is  constructed  after  the  fashion  of  an  ordinary  board  gate,  with 
horizontal  boards  and  openings  the  same  size  as  the  boards.  This  is 
placed  on  the  crest  of  the  advancing  dune  and  braced  in  two  direc¬ 
tions  with  poles.  As  the  fence  becomes  buried  it  is  raised  at  inter¬ 
vals;  and  since  the  fence  checks  the  advance  of  the  crest  of  the  dune 
the  advance  of  the  entire  dune  is  stopped.  (See  fig.  10). 

These  fences  have  been  in  practical  use  in  checking  the  advance  of 
dunes  along  the  Columbia  River,  where  they  were  a  danger  to  the 
railroad  right  of  way  and  to  valuable  irrigated  farm  lands.  Such 
fences  have  also  proved  very  valuable  in  retarding  the  formation 
of  large  blow-outs  and  in  filling  them  with  sand  blown  in  from 
elsewhere. 

SUMMARY. 

The  effect  of  wind  in  blowing  soils  is  in  the  aggregate  of  much 
importance  in  the  humid  sections,  although  the  process  is  slower  and 
less  obvious  than  in  the  drier  regions.  The  good  effect  of  the  shift¬ 
ing  of  soil  lies  in  the  mixing  of  the  soil  particles  and  the  renewing  of 
the  surface  layers.  The  evil  effects  occur  principally  in  the  arid  and 
semiarid  regions.  The  most  practical  means  of  control  lie  in  the 
proper  adjustment  of  the  cropping  and  tillage  system  so  as  to  pro¬ 
vide  at  the  critical  stages  a  protection  of  either  plants  or  rough  surface 
soil.  Increasing  the  humus  content  of  the  soil  also  reduces  the  danger 
of  blowing.  When  the  land  is  used  for  intensive  farming,  brush 
lines,  straw  covering,  hedges,  or  windbreaks  of  trees  constitute  the 
most  efficient  protection. 

421 


o 


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